Signal transmission system



Oct. 4, 1932. s. DOBA, JR 1,880,889

SIGNAL TRANSMISSION SYSTEM Filed May 25, 1931 I um W? T Q WWW- Q .3? N R; 5r

INVENTOR By S. DOBAJB.

ATTORNEY Patented Oct. 4, 1932 UNITED STATES STEPHEN DOBA, 33s., on NEW YORK, 1\T.*Y., ASSIGNOR 'i'o BELL TELEPHONE LABQRATORIES,

- YORK; N. Y., A oonroan'rron. on NEW YO K INCORPORATED, 013 NEW SIGNAL TRANSMISSION sYsrEr'r Application filed May -25,

This invention relates to signal transmis- "sion systems and particularly to control circults forlimiting the energy volume of signals transmitted over transmissionsystems. One object of the invention is to provide a signal transmission system that shall pre vent the energy volume at any desired point in the system rising above a predetermined limit and that shall insure against any control of the energy volume below said predetermined limit- Another object of the invention is to provide a signal transmission system with a loss device that at any desired point in the system shall not only prevent small peaks of energy volume rising above a predetermined limit but shall prevent the energy volume rising above saidlimit for extended periods while insuring against control of the ener y vol ume when below said predetermined limit.

A further object of the invention is to provide a signal transmissionv system having a three-element vacuum tube loss device that shall vary the negative grid biasing potential on the device according to the charge on two condensers of different sizes and that shall so control the charge on said-condensersas to prevent the energy volume in the system beyond the device rising above a predetermined limit.

In certain types of signal systems it is desirable to prevent the energy volume going above a predetermined limit without effecting any control to produce constant'volume. example of this type of system is a voice frequency carrier telegraph system. In order to protect transmission apparatus in such a system it is desirable to prevent isolated peaks of energy volume or extended periods of energy volume going above a predetermined limit;

In a signal system having volume control circuits constructed according to the present invention a transmitting. channel is provided with two loss devices comprising two threeelement vacuum tubesconnected in push-pull relationship. The negative grid bias on the loss device is controlled in accordance with the charge on a condenser in the grid circuits 1931. Serial No. 539,830.

and the charge on the relatively large condenser serves to prevent-extended periods of energy volume going above the predetermined limit. V Y

The two condensers which control the negative grid bias on the loss devices are charged in accordance with the predetermined limit by a clrcuit con neoted to the transmitting channel beyond the loss devices. A relay is provided for insuring the discharge of the two condensers whenever the energy volume on the transmitting channel beyond the loss devices is below said predetermined limit. trolled to etfect'dis'charge of the condensers at any desired .rate when the energy volume in the transmitting channel beyond the loss devices is below said predetermined limit.

A volume control circuit having three-element vacuum tube loss devices connected in push-pull relationship in a transmitting channel is disclosed in'the patent to SaDoba, N0.1,85l,828 dated April 19, 1932. A volume control circuit having a vacuum tube loss device controlled inv accordance with the charge on a condenser is disclosed in the patent-to J. L. Hogget al;,' No. 1,853,974 dated April 12,1932. v

The single figure in the accompanying drawing is .a diagrammatic view of a volume limiting circuit constructed in accordance wlth the invention;

means of a trans-former 6. The vacuum tube loss devices 4 and 5 are connected in the theenergy volume above The'relay is contransmitting channel in push-pull relationship and are connected to an amplifier tube 7 by means of a transformer 38. The amplifier tube 7 is connected to the outgoing conductors 8 and 9 by means of a transformer 10.

The negative grid bias on the loss devices 4 and I is not only controlled by'b'attery 11 but also by the charge on a small condenser 12 and the charge on a relatively. large 'eon- .denser 13. The condenser13 in iseries'with a resistance element 14 is connected linsliunt .to the condenser 12. Thecharge on t'hecondensers 12211101 13 is governed by aa' zcorrtrol circuit'connected to the transmitting channel 1 at a point beyond the loss devices 4 and 5. The control circuit which governsthe charge on the condensers 12 and -13 comprises two I rectifier tubes 15 and 16 andan amplifier tube hy a transformer 19. The output circuits of the rectifier tubes 15 and 16 are connected to the condensers Band 13.

A polarized relay 20 having a holding-coil 21 and an operating coil :22 is provided for discharging condensers 12 and 13 when :the energy volume on the transmitting channel beyond the loss devices 4 and 5 is below the predetermined limit. The operating coil'22 for the relay 20 is controlled by a' circuit connected to the output circuit of the amplifier 17 by means of a transformer 23. The

transformer 23 is connected to the operating coil of the relay 22 by means of a three-elevment rectifier tube 24.

A battery 25 is provided for supplying filament heating current to the rectifier tubes :16 and 24 and the loss device 5. A battery 2.6 is provided for supplying filament heating current to the rectifier tube 15,-jainplifier tubes 7 and 17 and the-loss device 4. A

battery 27 is provided forusupplying plate potential to theloss devices 4 and 5, a battery-28 is providedlfor supplying plate potential to the amplifier tubes 7 and 17,2 battery 29 is provided for supplying plate-potential for the rectifier tubes 15 and lfiian-d a battery 30 is provided for supplying plate potential to: the rectifier tube'24. A negative grid biasing battery 31 is provided for ithe two amplifier tubes 7 and 17. A negative grid biasing battery 32.is provided for the three rectifier tubes 15,716 and '24. I

When the transmitting channel isidle or devices is below the predetermined limit'the armature of the relay 20 is held in engagement with the contact member 33 by the bias ing coil 21.' The biasing coil 21 is energized from the battery30 in circuit with a resistance element 34. When the armature ofthe. I

mined limit for, an extended period of time.

relay is in engagement with the contact member 33 condensers 12 and 13 will be discharged through a resistance element 35. The size of the resistance element 35 may be varied according to the rate at which it is desired to have the condensers 12 and 13 discharged.

llnder' some conditions it ispossibie to dispense with the relay 2,0 and to permanently connect the resistance element 35 across the condensers 1 2 and .13- so as to discharge the condensers 12 andj13 at ja fixedrate at all times; i

T-he condenser 12 which is assumed to be of relatively small size is charged by small peak'sof energy volume above the predetermined limit. vThe condenser 13 which is assumed to be relatively large insize is charged when the' energy vol ume bey'on'd "the loss devices4 and 5 tendsto go aibovethe predetep Assuming signals on the transmitting channelyhaving small peaks of energy volume beyoridt'he loss devices whichex-tend abovethe 'predetermineddimit, the negative grid bias from the battery 31-on the amplifierftube '17 will be overcome to impress potential from the amplifier tube 17 on the input circuitsof the rectifier 'tu beslb and '16. The'negative grid bias on the rectifier tubes will be overcome to lower the internalresistance of the rectifier tubes15 and 16' and permitthe battery 29-to apply a charge for short periods of tim'e' on the condensers 1'2 and 1 3. The

condenser 12 which is relatively smailwiil "be charged very quickly to applya'negative potential to the-grids of the loss devices 4 ends thus increasing the interna l'impedance *of'such loss devices to prevent the peaks of energy volume beyond the loss devices'goi-ng' above the predetermined limit. The condenser 13 which is relatively large in size and which is connected in series with the resist ance element 14-will not be charged asthe condenser 12 is charged when-onlysmaill peakso'f energy volume extend above the pre- 7 determined limit on the transmitting channel beyond the loss devices4 and 5; When the energy'volume beyond the loss devices is {reduced the condenser :12 tends to discharge through the condenser 13 and to reduce' the negative biasing potential :on the gridsofthe loss devices4 and 5.'- Thisaction talres'pl-aee rapidly and is independent-of the dis'charge circuit controlled by the relay 20. At the same time the condenser. 12 is charged-the relay-20 is operatedgto break-the shunt circuit around the condenser 12 which extends through the arm ature pf "the relay and the when the energy volume levelbeyondthe loss resistance element .35.w Theioutput circuit a and 5 is prevented from extending above prising a condenser and a resistance element ll is connected across the output circuit of the rectifier tube2 i for governing the time of release of the relay 20. The size ofthe condenser 40 and the resistance element 41 may be varied to govern the time of release of therelayQO and accordingly the discharge of the condenser 12 or condenser 13 as the case may be.

If the energy volume on the transmitting channel beyond the loss devices 4- and 5 tends to go above the predetermined limit for an extended period of time the condenser 13 W111 be charged to approximately the same potential as the condenser '12. When the energy volume is reduced the potential on the condenser 12 will tend to be maintained for a longer period of time. The relay 20 is operated to break the'discharge circuit across the condensers l2 and 13 in the same manner as was described when reference was made to the charging of condenser 12. W hen the the predetermined limit while at the same time it is insured that no variation of the energy volume is eliected by the loss devices when theenergy volume on the conductors 8 and 9 is below said predetermined limit. It is apparent that a circuit might be constructed with condenser 12 only for controlling the l negative grid bias of the less devices 4 and 5 or with only the condenser 13 in series with the resistance element 14 for controlling the negative grid bias of the loss devices 4 and 5.

.However, in orderto take care of all con ditions of volume variationsabove the predetermined limit on the transmitting channel beyond the loss devices t and 5 it is pre ferred to employ a relatively small condenser 12 in combination with the relatively large condenser 13 in series with a resistance element. v

Modifications in the system in the arrangement and location of parts may be made within the spirit and scope of the specification and such modifications are intended to be covered by the appended claims.

lVhat is claimed is:

1. In a signal transmission system, a transmission line, a three-element vacuum tube loss device'connected in series with said line, means comprising a condenser connected in the grid circuit of said loss device for impressing a negative grid biasing potential thereon when charged, means for charging said condenser when the energy volume on the line beyond the loss device goes above a predetermined limit, and means for discharging saidcondenser when the energy volume on the line beyond the loss device falls below said predetermined limit. o

2. In a signal transmission system, a trans mission line, a three-element vacuum tube loss device connected to said line, means com-- prising a relatively small condenser connected in the grid circuit of said devicefor impressing a negative grid biasing potential thereon, means for controlling the charge on said condenser according to the energy volume on the line beyond the loss device to quickly charge the condenser and preventshort peaks of energy going above a predetermined limit, and means comprising a relay for discharging said condenser to prevent varying the energy volume beyond theloss device when-below said predetermined limit.

3. In asignal transmission system, a transmission line, a three-element vacuum tube loss device connected to said line, means comprising a relatively large condenser connected in series with a resistance element in the grid circuit of said loss device forimpressing v a negative grid biasing potential thereon, means for controlling the charge on said condenser according to the energy volume on the line beyond the loss device to relatively slowly charge the condenser and prevent prolonged periods of energy volume beyond the loss device above a predetermined limit, and means for so discharging said condenser when the energy volume beyond the loss device falls below said predetermined limit. 7 4. In a signal transmission system, a transmission line, a three-element vacuum tube loss device connected in series with said line, means comprising a condenser shunted by a relatively large condenser and a resistance element for applying a negative biasing potential to the grid of said device according to the charge on the condensers to vary the loss causedby the device, and means for controlling the charge on said condensers according to the energy volume on the .line beyond the loss device to prevent the energy volume beyond the device going above a predetermined limit while insuring against change in the energy volume when below the predetermined limit.

5. In a signal transmission system, a transmission line, a three-element vacuum tube loss device connected to said line, means comprising a relativelylarge condenser and a relatively small condenser for controlling the negative biasing potential on the grid of said device to govern the loss in said line, means governed by the energy volume on the line beyond said loss device for charging said small condenser quickly to prevent small V and for chargingthe large condenser at a v mined limit.

v slower rateby large volume changes to maintain the rene'rgy volume below said lpredec termined limit, and, means for discharging said condensers when theenergyvolume .beyond the loss device is below said predeter- (ii In a signal transmission system, atransmission line, two three-element vacuum tube loss devices connected in push-pull relationship'in said line, means comprising a'condenser connected in the grid circuits of said loss devices for impressing a negative grid biasing potential on. the tubeswhen acharge is impressed tliereon, means for charging said condenser when the energy volume on vthe line beyond the loss devices goes above a predetermined liinit, and means for insuring the discharge of said condenser when the energy volume on the line beyond the loss device falls below said predetermined limit.

7. In a signal transmission systenna transmission line, two three-element vacuum tube loss devicesconnected in push-pull relationship insaid line, means comprising a condenser shunted by a relativelylarge condenser in series with aresistance element for applying a negative grid biasing potential to said devices according to the changeon the condensers to vary. the loss caused by the devices, and means for controlling the charge on said condensers according to the energy volume on theline beyond the loss 1 devices toprevent the energyivolume beyond the device going above a predetermined limitwhile insuring the discharge of the condensers when the energy volume on the line beyond the loss devices falls below said predetermined limit. a

8. In a signal transmission systeni,.a,transmission line, two three element vacuum tube 'lo'ss devices connected in piisi -pull relationship in said line, means comprising a relatively small condenser connectedin the grid circuit of said devices for impressing a negative grid bias ng potent al thereon, r neans for controlling'the charge on said condenser according to the energy volume oiithe l ne' beyond the loss devices to quickly chargethe condenser and prevent short peaksof energy going above a predetermined limit, and neans comprisinga relay for insuring the discharge of'said condenser when the energy volume on the line beyond the loss devices falls below said predeterminedl mit.

9. In a signal transmiss on system, at 'ai smission line, a loss dev ce connected ,inseries with said line, means comprising a condenser for controlling said device to vary the loss causedthereby in accordance with the-charge on the condenser, means for charging said condenserwhen the energy volume on theline beyond the device goes above apredetermined limit, and means for insuring a quick dis- .charge offsaid condenser-when the energy said predetermined limit. v v i V n a i na transm i ystem, ia transmission line,aloss device connected in Series wi sa m a -Qmpri n a condenser shunted by a relat ively large cons s in e esW l ares stan l ment 9 tr g a d v ce t raryitb le ause thereby in accordance with th chargennthe c nd n e mean p she-reliessaid p d n e s wh n the e rgy v lt me .0 the lin ;b y0n -t1ie devic goe absr a sm les i m d m tan m an e c i siirinsraiquic d a g d s id condense -Wh n th -en rgy volume beyond the loss device falls ;b ,e lo,vv

Sai p d erm ned imi 1 ;1-1. In a signal transmission systemfltransmission ine, a threeseleine r dium-tube loss, deviceconnectedito said line, means,co mprising a condenser. :for impressingva negative olume b yond th lo d i e a lebele grid :biasing potential von the loss; vdevice,

means for controlling-the charge ,011 said, condenser accordin totheenergy Ivolunieonrthe line beyond the loss device, means. comprising a relay for dischargingsaid condenser when the energy volume onthe:lineflbeyondthe-loss device falls :below, said predetermined limit,

.and means for controlling .thetimeof opera- "tion oisaidirelayupon lowering of ,therenergy volume on .thefline .below said predetermined .pedance ineans connected in said circuit for I V governing the energy volume in this vcircuit.

beyond the impedance means, quicleacting means vautomatically controlled according to the energy volume on said circuit beyond the impedance means ion-governing said-impedance-means to prevent peaksnof energy in said circuitgoing abovea predetermined-"limit and slower-acting means automatically-controlled according tot-he energy volume on said circuit'beyondthe'impedance means for'governing said impedance means to prevent pro longed periods of energy volume onjsaid circuit going above the predetermined energy limit. I "I v 1 .s sna' v ys niia g al i itimre an mean c nne ed in sai circu t governing the energy volume in this circi it b yon th impe an m ans, a iskractiegc m a s au mati a-Hy On.tro 1,e a prd a t h e gye qlume isa e ia igore ni g said impedance means to prevent peaks of energy in said circuit going above a predetermined limit, and means for insuring against control of the impedance means by said quick-acting means when the peaks of energy volume fall below the predetermined limit.

15. In a signal transmission system, a transmission'line, an impedance device connected in said line for limiting the amplitude of the signal waves, control means governed by the energy waves on the signal line beyond the impedance device for operating said device to prevent the signal waves going above a predetermined upper limit, and means for insuring against control of the amplitude of the signal waves by the device when the amplitude of the signal waves falls below the predetermined upper limit.

In witness whereof, I hereunto subscribe my name this 21st day of May, 1931.

STEPHEN DOBA', JR. 

